The present invention relates generally to devices for holding and maintaining a tool or instrument in pre-selected positions. More specifically, the present invention relates to a lockable, adjustable holder for supporting and maintaining a surgical tool or instrument in a desired or selected position.
Surgical procedures often require that a tool or instrument be maintained in a pre-selected position and/or apply a constant force to a tissue or organ. The limited area and generally restricted access to most surgical sites on a patient in an operating room or theatre, however, makes it desirable that as few operating theatre personnel as possible surround the patient, thus generally precluding theatre assistants from holding each and every tool. Mechanical holders, therefore, are a preferred choice for holding tools or instruments, offering stability and a compactness that a human assistant cannot provide.
During most surgical procedures, tools or instruments attached to mechanical holders typically have to be constantly adjusted relative to the surgical site, or moved or removed from the surgical site depending on the immediate needs of the operating surgeon. Again, the confined working area demands the minimum number of active persons be present to adjust and reposition the holding devices. There is, therefore, a clear advantage in having tools or instrument holders that can be easily manipulated solely by the surgeon. The workload demands placed upon the surgeon, however, require that the apparatus be operated with a minimum of effort and distraction. Further, since any equipment used in surgery will be in the sterile environment of an operating theatre, mechanical holders also must be able to tolerate sterilization, especially by autoclaving. A simple, sterilizable device that can be adjusted to different positions and be locked into place with a simple operation, demanding little attention from the surgeon is, therefore, highly desirable.
A typical use for an adjustable and releasably lockable instrument holder is in the field of neurosurgery where the brain, or a region thereof, must be retracted or pulled back to allow access to underlying tissue. A blade retractor typically is used in this technique, and may generally be held in position by a surgical assistant. When most conventional brain retractors or holders are held by an assistant, however, there is the potential for shifting or movement of the retractor because of instability of the assistant, or fatigue.
A number of brain retractors and holding apparatus are known in the art. McEwen et al, for example, in U.S. Pat. No. 5,201,325, discloses a pneumatically operating adjustable apparatus comprising several elongated links that are lockable into a pre-selected position. This apparatus requires multiple connections to pressure and pressure sensing apparatus that introduce a complex of wiring to the already crowded surgical environment.
Another conventional lockable instrument holder is the xe2x80x9cGreenbergxe2x80x9d brain retractor consisting of a plurality of ball and socket joints threaded on a length of cable. When the cable is tightened by a lever mechanism, the friction within each ball and socket is increased and the retraction arm becomes rigid. Limited friction in the ball and socket joints of this device, however, tends to limit the weight of the tool or instrument that can be carried by the retractor. The xe2x80x9cGreenbergxe2x80x9d retractor further requires that the operator, such as the surgeon, manipulate a mechanical screw means for tightening the cable to lock the retractor in place, which consequently requires a distractive and lengthy drawing of attention away from the surgery.
There is still a need, therefore, for a simple, easily operated surgical tool or instrument holder that will allow a surgeon to position a tool such as a brain retractor and then lock the tool into a substantially fixed, selected position with a minimum of effort.
Briefly described, the present invention comprises a releasably lockable adjustable instrument holding mechanism for rigidly maintaining a tool or instrument in a pre-selected orientation that will allow a surgeon to position and substantially fix the surgical instrument easily and without extensive or distracting manipulation of a complex locking mechanism. In one aspect of the present invention, the instrument holding mechanism generally comprises an actuatable arm attached to a tensioning cable and a tensioning device having an actuator housing defining an interior cavity and an actuator mechanism such as a conductive wire element. The tensioning cable passes through a duct in the actuator housing communicating with the interior cavity, and the proximal end of the tensioning cable operably connects to at least one electrically conductive wire that is connected to the actuator housing. The tensioning device is pivotally connected to an articulated arm by a hinged joint.
In one aspect of the present invention, the articulated arm includes a plurality of links longitudinally arranged along a common axis, with adjacent links being pivotally connected by a hinged joint. Each link has a lumen or central cavity or duct longitudinally arranged along the common axis so as to define a longitudinally extending passage or duct along the length of the arm. The tensioning cable is slideably disposed within the duct of the arm and through the duct and interior cavity of the actuator housing, and has a distal end attached to the distal end of the articulated arm and a proximal end operably attached to the tensioning device.
In one aspect of the present invention, once the articulated arm has been adjusted to a desired, pre-selected holding position, the tensioning device is engaged, causing an electric current to be passed through the conductive wire, which heats and contracts, thereby applying a tension force to the tensioning cable. This tension force compresses the hinged joints of the articulated arm, so as to rigidly lock the arm into the desired preset position. A switch is provided along with the housing to enable the operator to automatically activate or deactivate the tensioning cable to thus lock or unlock the articulated arm.
In another aspect of the present invention, the instrument holder can further include a frame slideably disposed in the actuator housing of the tensioning device and which is rotatably connected to a tensioning rod having a screw thread thereon. The tensioning device further will typically include an electric motor or similar motorized device and a worm gear or screw, wherein the gear is operably connected to the screw thread of the tensioning rod. The motor is connected to a power source and a switch.
In yet another aspect of the present invention the frame can be slideably disposed in the interior cavity of the actuator housing and will include a threaded hole. The motor of the tensioning device can also include a shaft with a screw thread disposed thereon that operably connects to the threaded hole of the frame.
In addition, the hinged joints of the articulated arm generally will have contacting surfaces having a surface coating such as a bonded tungsten carbide layer thereon. The hinged joints also may have uneven contacting surfaces to increase the strength of the locking action to rigidly maintain the articulated arm in its pre-selected orientation.
It further is contemplated that in all aspects of the present invention, a surgical tool or instrument may be attached to the articulated arm. In particular, the releasably lockable arm of the present invention may be used to rigidly maintain a brain retractor in a desired, selected position, and subsequently released for removal of the retractor from the brain of a patient by the simple operation of a switch. It is within the scope of the present invention, however, that the lockable articulated arm may be connected to a variety of tools or instruments of different sizes and shapes including devices outside the surgical field that are to be maintained at a pre-selected orientation.
Various objects, features, and advantages of the invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawing figures, which are briefly described as follows.